<?php
/*
* 2007-2015 PrestaShop
*
* NOTICE OF LICENSE
*
* This source file is subject to the Open Software License (OSL 3.0)
* that is bundled with this package in the file LICENSE.txt.
* It is also available through the world-wide-web at this URL:
* http://opensource.org/licenses/osl-3.0.php
* If you did not receive a copy of the license and are unable to
* obtain it through the world-wide-web, please send an email
* to license@prestashop.com so we can send you a copy immediately.
*
* DISCLAIMER
*
* Do not edit or add to this file if you wish to upgrade PrestaShop to newer
* versions in the future. If you wish to customize PrestaShop for your
* needs please refer to http://www.prestashop.com for more information.
*
*  @author PrestaShop SA <contact@prestashop.com>
*  @copyright  2007-2015 PrestaShop SA
*  @license    http://opensource.org/licenses/osl-3.0.php  Open Software License (OSL 3.0)
*  International Registered Trademark & Property of PrestaShop SA
*/

if (file_exists(_PS_ROOT_DIR_.'/config/settings.inc.php'))
	include_once(_PS_ROOT_DIR_.'/config/settings.inc.php');

/**
 * Class DbCore
 */
abstract class DbCore
{
	/** @var int Constant used by insert() method */
	const INSERT = 1;

	/** @var int Constant used by insert() method */
	const INSERT_IGNORE = 2;

	/** @var int Constant used by insert() method */
	const REPLACE = 3;

	/** @var int Constant used by insert() method */
	const ON_DUPLICATE_KEY = 4;

	/** @var string Server (eg. localhost) */
	protected $server;

	/**  @var string Database user (eg. root) */
	protected $user;

	/** @var string Database password (eg. can be empty !) */
	protected $password;

	/** @var string Database name */
	protected $database;

	/** @var bool */
	protected $is_cache_enabled;

	/** @var PDO|mysqli|resource Resource link */
	protected $link;

	/** @var PDOStatement|mysqli_result|resource|bool SQL cached result */
	protected $result;

	/** @var array List of DB instances */
	public static $instance = array();

	/** @var array List of server settings */
	public static $_servers = array();

	/** @var null Flag used to load slave servers only once.
	 * See loadSlaveServers() method.
	 */
	public static $_slave_servers_loaded = null;

	/**
	 * Store last executed query
	 *
	 * @var string
	 */
	protected $last_query;

	/**
	 * Store hash of the last executed query
	 *
	 * @var string
	 */
	protected $last_query_hash;

	/**
	 * Last cached query
	 *
	 * @var string
	 */
	protected $last_cached;

	/**
	 * Opens a database connection
	 *
	 * @return PDO|mysqli|resource
	 */
	abstract public function connect();

	/**
	 * Closes database connection
	 */
	abstract public function disconnect();

	/**
	 * Execute a query and get result resource
	 *
	 * @param string $sql
	 * @return PDOStatement|mysqli_result|resource|bool
	 */
	abstract protected function _query($sql);

	/**
	 * Get number of rows in a result
	 *
	 * @param mixed $result
	 * @return int
	 */
	abstract protected function _numRows($result);

	/**
	 * Get the ID generated from the previous INSERT operation
	 *
	 * @return int|string
	 */
	abstract public function Insert_ID();

	/**
	 * Get number of affected rows in previous database operation
	 *
	 * @return int
	 */
	abstract public function Affected_Rows();

	/**
	 * Get next row for a query which does not return an array
	 *
	 * @param PDOStatement|mysqli_result|resource|bool $result
	 * @return array|object|false|null
	 */
	abstract public function nextRow($result = false);

	/**
	 * Get all rows for a query which return an array
	 *
	 * @param PDOStatement|mysqli_result|resource|bool|null $result
	 * @return array
	 */
	abstract protected function getAll($result = false);

	/**
	 * Get database version
	 *
	 * @return string
	 */
	abstract public function getVersion();

	/**
	 * Protect string against SQL injections
	 *
	 * @param string $str
	 * @return string
	 */
	abstract public function _escape($str);

	/**
	 * Returns the text of the error message from previous database operation
	 *
	 * @return string
	 */
	abstract public function getMsgError();

	/**
	 * Returns the number of the error from previous database operation
	 *
	 * @return int
	 */
	abstract public function getNumberError();

	/**
	 * Sets the current active database on the server that's associated with the specified link identifier.
	 * Do not remove, useful for some modules.
	 *
	 * @param string $db_name
	 * @return bool|int
	 */
	abstract public function set_db($db_name);

	/**
	 * Selects best table engine.
	 *
	 * @return string
	 */
	abstract public function getBestEngine();

	/**
	 * Returns database object instance.
	 *
	 * @param bool $master Decides whether the connection to be returned by the master server or the slave server
	 * @return Db Singleton instance of Db object
	 */
	public static function getInstance($master = true)
	{
		static $id = 0;

		// This MUST not be declared with the class members because some defines (like _DB_SERVER_) may not exist yet (the constructor can be called directly with params)
		if (!self::$_servers)
			self::$_servers = array(
				array('server' => _DB_SERVER_, 'user' => _DB_USER_, 'password' => _DB_PASSWD_, 'database' => _DB_NAME_), /* MySQL Master server */
			);

		if (!$master)
			Db::loadSlaveServers();

		$total_servers = count(self::$_servers);
		if ($master || $total_servers == 1)
			$id_server = 0;
		else
		{
			$id++;
			$id_server = ($total_servers > 2 && ($id % $total_servers) != 0) ? $id % $total_servers : 1;
		}

		if (!isset(self::$instance[$id_server]))
		{
			$class = Db::getClass();
			self::$instance[$id_server] = new $class(
				self::$_servers[$id_server]['server'],
				self::$_servers[$id_server]['user'],
				self::$_servers[$id_server]['password'],
				self::$_servers[$id_server]['database']
			);
		}

		return self::$instance[$id_server];
	}

	/**
	 * @param $test_db Db
	 * Unit testing purpose only
	 */
	public static function setInstanceForTesting($test_db)
	{
		self::$instance[0] = $test_db;
	}

	/**
	 * Unit testing purpose only
	 */
	public static function deleteTestingInstance()
	{
		self::$instance = array();
	}

	/**
	 * Loads configuration settings for slave servers if needed.
	 */
	protected static function loadSlaveServers()
	{
		if (self::$_slave_servers_loaded !== null)
			return;

		// Add here your slave(s) server(s) in this file
		if (file_exists(_PS_ROOT_DIR_.'/config/db_slave_server.inc.php'))
			self::$_servers = array_merge(self::$_servers, require(_PS_ROOT_DIR_.'/config/db_slave_server.inc.php'));

		self::$_slave_servers_loaded = true;
	}

	/**
	 * Returns the best child layer database class.
	 *
	 * @return string
	 */
	public static function getClass()
	{
		$class = 'MySQL';
		if (PHP_VERSION_ID >= 50200 && extension_loaded('pdo_mysql'))
			$class = 'DbPDO';
		elseif (extension_loaded('mysqli'))
			$class = 'DbMySQLi';

		return $class;
	}

	/**
	 * Instantiates a database connection
	 *
	 * @param string $server Server address
	 * @param string $user User login
	 * @param string $password User password
	 * @param string $database Database name
	 * @param bool $connect If false, don't connect in constructor (since 1.5.0.1)
	 */
	public function __construct($server, $user, $password, $database, $connect = true)
	{
		$this->server = $server;
		$this->user = $user;
		$this->password = $password;
		$this->database = $database;
		$this->is_cache_enabled = (defined('_PS_CACHE_ENABLED_')) ? _PS_CACHE_ENABLED_ : false;

		if (!defined('_PS_DEBUG_SQL_'))
			define('_PS_DEBUG_SQL_', false);

		if ($connect)
			$this->connect();
	}

	/**
	 * Disable the use of the cache
	 *
	 */
	public function disableCache()
	{
		$this->is_cache_enabled = false;
	}

	/**
	 * Enable & flush the cache
	 *
	 */
	public function enableCache()
	{
		$this->is_cache_enabled = true;
		Cache::getInstance()->flush();
	}

	/**
	 * Closes connection to database
	 */
	public function __destruct()
	{
		if ($this->link)
			$this->disconnect();
	}

	/**
	 * Executes SQL query based on selected type
	 *
	 * @deprecated 1.5.0.1 Use insert() or update() method instead.
	 * @param string $table
	 * @param array $data
	 * @param string $type (INSERT, INSERT IGNORE, REPLACE, UPDATE).
	 * @param string $where
	 * @param int $limit
	 * @param bool $use_cache
	 * @param bool $use_null
	 * @return bool
	 * @throws PrestaShopDatabaseException
	 */
	public function autoExecute($table, $data, $type, $where = '', $limit = 0, $use_cache = true, $use_null = false)
	{
		$type = strtoupper($type);
		switch ($type)
		{
			case 'INSERT' :
				return $this->insert($table, $data, $use_null, $use_cache, Db::INSERT, false);

			case 'INSERT IGNORE' :
				return $this->insert($table, $data, $use_null, $use_cache, Db::INSERT_IGNORE, false);

			case 'REPLACE' :
				return $this->insert($table, $data, $use_null, $use_cache, Db::REPLACE, false);

			case 'UPDATE' :
				return $this->update($table, $data, $where, $limit, $use_null, $use_cache, false);

			default :
				throw new PrestaShopDatabaseException('Wrong argument (miss type) in Db::autoExecute()');
		}
	}

	/**
	 * Filter SQL query within a blacklist
	 *
	 * @param string $table Table where insert/update data
	 * @param array $values Data to insert/update
	 * @param string $type INSERT or UPDATE
	 * @param string $where WHERE clause, only for UPDATE (optional)
	 * @param int $limit LIMIT clause (optional)
	 * @return bool
	 * @throws PrestaShopDatabaseException
	 */
	public function autoExecuteWithNullValues($table, $values, $type, $where = '', $limit = 0)
	{
		return $this->autoExecute($table, $values, $type, $where, $limit, 0, true);
	}

	/**
	 * Execute a query and get result resource
	 *
	 * @param string|DbQuery $sql
	 * @return bool|mysqli_result|PDOStatement|resource
	 * @throws PrestaShopDatabaseException
	 */
	public function query($sql)
	{
		if ($sql instanceof DbQuery)
			$sql = $sql->build();

		$this->result = $this->_query($sql);

		if (!$this->result && $this->getNumberError() == 2006)
		{
			if ($this->connect())
				$this->result = $this->_query($sql);
		}

		if (_PS_DEBUG_SQL_)
			$this->displayError($sql);

		return $this->result;
	}

	/**
	 * Executes an INSERT query
	 *
	 * @param string $table Table name without prefix
	 * @param array $data Data to insert as associative array. If $data is a list of arrays, multiple insert will be done
	 * @param bool $null_values If we want to use NULL values instead of empty quotes
	 * @param bool $use_cache
	 * @param int $type Must be Db::INSERT or Db::INSERT_IGNORE or Db::REPLACE
	 * @param bool $add_prefix Add or not _DB_PREFIX_ before table name
	 * @return bool
	 * @throws PrestaShopDatabaseException
	 */
	public function insert($table, $data, $null_values = false, $use_cache = true, $type = Db::INSERT, $add_prefix = true)
	{
		if (!$data && !$null_values)
			return true;

		if ($add_prefix)
			$table = _DB_PREFIX_.$table;

		if ($type == Db::INSERT)
			$insert_keyword = 'INSERT';
		elseif ($type == Db::INSERT_IGNORE)
			$insert_keyword = 'INSERT IGNORE';
		elseif ($type == Db::REPLACE)
			$insert_keyword = 'REPLACE';
		elseif ($type == Db::ON_DUPLICATE_KEY)
			$insert_keyword = 'INSERT';
		else
			throw new PrestaShopDatabaseException('Bad keyword, must be Db::INSERT or Db::INSERT_IGNORE or Db::REPLACE');

		// Check if $data is a list of row
		$current = current($data);
		if (!is_array($current) || isset($current['type']))
			$data = array($data);

		$keys = array();
		$values_stringified = array();
		$first_loop = true;
		$duplicate_key_stringified = '';
		foreach ($data as $row_data)
		{
			$values = array();
			foreach ($row_data as $key => $value)
			{
				if (!$first_loop)
				{
					// Check if row array mapping are the same
					if (!in_array("`$key`", $keys))
						throw new PrestaShopDatabaseException('Keys form $data subarray don\'t match');

					if ($duplicate_key_stringified != '')
						throw new PrestaShopDatabaseException('On duplicate key cannot be used on insert with more than 1 VALUE group');
				}
				else
					$keys[] = '`'.bqSQL($key).'`';

				if (!is_array($value))
					$value = array('type' => 'text', 'value' => $value);
				if ($value['type'] == 'sql')
					$values[] = $string_value = $value['value'];
				else
					$values[] = $string_value = $null_values && ($value['value'] === '' || is_null($value['value'])) ? 'NULL' : "'{$value['value']}'";

				if ($type == Db::ON_DUPLICATE_KEY)
					$duplicate_key_stringified .= '`'.bqSQL($key).'` = '.$string_value.',';
			}
			$first_loop = false;
			$values_stringified[] = '('.implode(', ', $values).')';
		}
		$keys_stringified = implode(', ', $keys);

		$sql = $insert_keyword.' INTO `'.$table.'` ('.$keys_stringified.') VALUES '.implode(', ', $values_stringified);
		if ($type == Db::ON_DUPLICATE_KEY)
			$sql .= ' ON DUPLICATE KEY UPDATE '.substr($duplicate_key_stringified, 0, -1);

		return (bool)$this->q($sql, $use_cache);
	}

	/**
	 * Executes an UPDATE query
	 *
	 * @param string $table Table name without prefix
	 * @param array $data Data to insert as associative array. If $data is a list of arrays, multiple insert will be done
	 * @param string $where WHERE condition
	 * @param int $limit
	 * @param bool $null_values If we want to use NULL values instead of empty quotes
	 * @param bool $use_cache
	 * @param bool $add_prefix Add or not _DB_PREFIX_ before table name
	 * @return bool
	 */
	public function update($table, $data, $where = '', $limit = 0, $null_values = false, $use_cache = true, $add_prefix = true)
	{
		if (!$data)
			return true;

		if ($add_prefix)
			$table = _DB_PREFIX_.$table;

		$sql = 'UPDATE `'.bqSQL($table).'` SET ';
		foreach ($data as $key => $value)
		{
			if (!is_array($value))
				$value = array('type' => 'text', 'value' => $value);
			if ($value['type'] == 'sql')
				$sql .= '`'.bqSQL($key)."` = {$value['value']},";
			else
				$sql .= ($null_values && ($value['value'] === '' || is_null($value['value']))) ? '`'.bqSQL($key).'` = NULL,' : '`'.bqSQL($key)."` = '{$value['value']}',";
		}

		$sql = rtrim($sql, ',');
		if ($where)
			$sql .= ' WHERE '.$where;
		if ($limit)
			$sql .= ' LIMIT '.(int)$limit;

		return (bool)$this->q($sql, $use_cache);
	}

	/**
	 * Executes a DELETE query
	 *
	 * @param string $table Name of the table to delete
	 * @param string $where WHERE clause on query
	 * @param int $limit Number max of rows to delete
	 * @param bool $use_cache Use cache or not
	 * @param bool $add_prefix Add or not _DB_PREFIX_ before table name
	 * @return bool
	 */
	public function delete($table, $where = '', $limit = 0, $use_cache = true, $add_prefix = true)
	{
		if (_DB_PREFIX_ && !preg_match('#^'._DB_PREFIX_.'#i', $table) && $add_prefix)
			$table = _DB_PREFIX_.$table;

		$this->result = false;
		$sql = 'DELETE FROM `'.bqSQL($table).'`'.($where ? ' WHERE '.$where : '').($limit ? ' LIMIT '.(int)$limit : '');
		$res = $this->query($sql);
		if ($use_cache && $this->is_cache_enabled)
			Cache::getInstance()->deleteQuery($sql);

		return (bool)$res;
	}

	/**
	 * Executes a query
	 *
	 * @param string|DbQuery $sql
	 * @param bool $use_cache
	 * @return bool
	 */
	public function execute($sql, $use_cache = true)
	{
		if ($sql instanceof DbQuery)
			$sql = $sql->build();

		$this->result = $this->query($sql);
		if ($use_cache && $this->is_cache_enabled)
			Cache::getInstance()->deleteQuery($sql);

		return (bool)$this->result;
	}

	/**
	 * Executes return the result of $sql as array
	 *
	 * @param string|DbQuery $sql Query to execute
	 * @param bool $array Return an array instead of a result object (deprecated since 1.5.0.1, use query method instead)
	 * @param bool $use_cache
	 * @return array|false|null|mysqli_result|PDOStatement|resource
	 * @throws PrestaShopDatabaseException
	 */
	public function executeS($sql, $array = true, $use_cache = true)
	{
		if ($sql instanceof DbQuery)
			$sql = $sql->build();

		$this->result = false;
		$this->last_query = $sql;

		if ($use_cache && $this->is_cache_enabled && $array)
		{
			$this->last_query_hash = Tools::encryptIV($sql);
			if (($result = Cache::getInstance()->get($this->last_query_hash)) !== false)
			{
				$this->last_cached = true;
				return $result;
			}
		}

		// This method must be used only with queries which display results
		if (!preg_match('#^\s*\(?\s*(select|show|explain|describe|desc)\s#i', $sql))
		{
			if (defined('_PS_MODE_DEV_') && _PS_MODE_DEV_)
				throw new PrestaShopDatabaseException('Db->executeS() must be used only with select, show, explain or describe queries');
			return $this->execute($sql, $use_cache);
		}

		$this->result = $this->query($sql);

		if (!$this->result)
			$result = false;
		else
		{
			if (!$array)
			{
				$use_cache = false;
				$result = $this->result;
			}
			else
				$result = $this->getAll($this->result);
		}

		$this->last_cached = false;
		if ($use_cache && $this->is_cache_enabled && $array)
			Cache::getInstance()->setQuery($sql, $result);

		return $result;
	}

	/**
	 * Returns an associative array containing the first row of the query
	 * This function automatically adds "LIMIT 1" to the query
	 *
	 * @param string|DbQuery $sql the select query (without "LIMIT 1")
	 * @param bool $use_cache Find it in cache first
	 * @return array|bool|object|null
	 */
	public function getRow($sql, $use_cache = true)
	{
		if ($sql instanceof DbQuery)
			$sql = $sql->build();

		$sql = rtrim($sql, " \t\n\r\0\x0B;").' LIMIT 1';
		$this->result = false;
		$this->last_query = $sql;

		if ($use_cache && $this->is_cache_enabled)
		{
			$this->last_query_hash = Tools::encryptIV($sql);
			if (($result = Cache::getInstance()->get($this->last_query_hash)) !== false)
			{
				$this->last_cached = true;
				return $result;
			}
		}

		$this->result = $this->query($sql);
		if (!$this->result)
			$result = false;
		else
			$result = $this->nextRow($this->result);

		$this->last_cached = false;

		if (is_null($result))
			$result = false;

		if ($use_cache && $this->is_cache_enabled)
			Cache::getInstance()->setQuery($sql, $result);

		return $result;
	}

	/**
	 * Returns a value from the first row, first column of a SELECT query
	 *
	 * @param string|DbQuery $sql
	 * @param bool $use_cache
	 * @return string|false|null
	 */
	public function getValue($sql, $use_cache = true)
	{
		if ($sql instanceof DbQuery)
			$sql = $sql->build();

		if (!$result = $this->getRow($sql, $use_cache))
			return false;

		return array_shift($result);
	}

	/**
	 * Get number of rows for last result
	 *
	 * @return int
	 */
	public function numRows()
	{
		if (!$this->last_cached && $this->result)
		{
			$nrows = $this->_numRows($this->result);
			if ($this->is_cache_enabled)
				Cache::getInstance()->set($this->last_query_hash.'_nrows', $nrows);
			return $nrows;
		}
		elseif ($this->is_cache_enabled && $this->last_cached)
			return Cache::getInstance()->get($this->last_query_hash.'_nrows');
	}

	/**
	 * Executes a query
	 *
	 * @param string|DbQuery $sql
	 * @param bool $use_cache
	 * @return bool|mysqli_result|PDOStatement|resource
	 * @throws PrestaShopDatabaseException
	 */
	protected function q($sql, $use_cache = true)
	{
		if ($sql instanceof DbQuery)
			$sql = $sql->build();

		$this->result = false;
		$result = $this->query($sql);
		if ($use_cache && $this->is_cache_enabled)
			Cache::getInstance()->deleteQuery($sql);

		if (_PS_DEBUG_SQL_)
			$this->displayError($sql);

		return $result;
	}

	/**
	 * Displays last SQL error
	 *
	 * @param string|bool $sql
	 * @throws PrestaShopDatabaseException
	 */
	public function displayError($sql = false)
	{
		global $webservice_call;

		$errno = $this->getNumberError();
		if ($webservice_call && $errno)
		{
			$dbg = debug_backtrace();
			WebserviceRequest::getInstance()->setError(500, '[SQL Error] '.$this->getMsgError().'. From '.(isset($dbg[3]['class']) ? $dbg[3]['class'] : '').'->'.$dbg[3]['function'].'() Query was : '.$sql, 97);
		}
		elseif (_PS_DEBUG_SQL_ && $errno && !defined('PS_INSTALLATION_IN_PROGRESS'))
		{
			if ($sql)
				throw new PrestaShopDatabaseException($this->getMsgError().'<br /><br /><pre>'.$sql.'</pre>');

			throw new PrestaShopDatabaseException($this->getMsgError());
		}
	}

    /**
     * Sanitize data which will be injected into SQL query
     *
     * @param string $string SQL data which will be injected into SQL query
     * @param bool $html_ok Does data contain HTML code ? (optional)
     * @return string Sanitized data
     */
	public function escape($string, $html_ok = false, $bq_sql = false)
	{
		if (_PS_MAGIC_QUOTES_GPC_)
			$string = stripslashes($string);

		if (!is_numeric($string))
		{
			$string = $this->_escape($string);

			if (!$html_ok)
				$string = strip_tags(Tools::nl2br($string));

			if ($bq_sql === true)
				$string = str_replace('`', '\`', $string);
		}

		return $string;
	}

	/**
	 * Try a connection to the database
	 *
	 * @param string $server Server address
	 * @param string $user Login for database connection
	 * @param string $pwd Password for database connection
	 * @param string $db Database name
	 * @param bool $new_db_link
	 * @param string|bool $engine
	 * @param int $timeout
	 * @return int Error code or 0 if connection was successful
	 */
	public static function checkConnection($server, $user, $pwd, $db, $new_db_link = true, $engine = null, $timeout = 5)
	{
		return call_user_func_array(array(Db::getClass(), 'tryToConnect'), array($server, $user, $pwd, $db, $new_db_link, $engine, $timeout));
	}

	/**
	 * Try a connection to the database and set names to UTF-8
	 *
	 * @param string $server Server address
	 * @param string $user Login for database connection
	 * @param string $pwd Password for database connection
	 * @return bool
	 */
	public static function checkEncoding($server, $user, $pwd)
	{
		return call_user_func_array(array(Db::getClass(), 'tryUTF8'), array($server, $user, $pwd));
	}

	/**
	 * Try a connection to the database and check if at least one table with same prefix exists
	 *
	 * @param string $server Server address
	 * @param string $user Login for database connection
	 * @param string $pwd Password for database connection
	 * @param string $db Database name
	 * @param string $prefix Tables prefix
	 * @return bool
	 */
	public static function hasTableWithSamePrefix($server, $user, $pwd, $db, $prefix)
	{
		return call_user_func_array(array(Db::getClass(), 'hasTableWithSamePrefix'), array($server, $user, $pwd, $db, $prefix));
	}

	/**
	 * Tries to connect to the database and create a table (checking creation privileges)
	 *
	 * @param string $server
	 * @param string $user
	 * @param string $pwd
	 * @param string $db
	 * @param string $prefix
	 * @param string|null $engine Table engine
	 * @return bool|string True, false or error
	 */
	public static function checkCreatePrivilege($server, $user, $pwd, $db, $prefix, $engine = null)
	{
		return call_user_func_array(array(Db::getClass(), 'checkCreatePrivilege'), array($server, $user, $pwd, $db, $prefix, $engine));
	}

	/**
	 * Checks if auto increment value and offset is 1
	 *
	 * @param string $server
	 * @param string $user
	 * @param string $pwd
	 * @return bool
	 */
	public static function checkAutoIncrement($server, $user, $pwd)
	{
		return call_user_func_array(array(Db::getClass(), 'checkAutoIncrement'), array($server, $user, $pwd));
	}

	/**
	 * Executes a query
	 *
	 * @deprecated 1.5.0.1
	 * @param string|DbQuery $sql
	 * @param bool $use_cache
	 * @return array|bool|mysqli_result|PDOStatement|resource
	 * @throws PrestaShopDatabaseException
	 */
	public static function s($sql, $use_cache = true)
	{
		Tools::displayAsDeprecated();
		return Db::getInstance()->executeS($sql, true, $use_cache);
	}

	/**
	 * Executes a query
	 *
	 * @deprecated 1.5.0.1
	 * @param $sql
	 * @param int $use_cache
	 * @return array|bool|mysqli_result|PDOStatement|resource
	 */
	public static function ps($sql, $use_cache = 1)
	{
		Tools::displayAsDeprecated();
		$ret = Db::s($sql, $use_cache);
		return $ret;
	}

	/**
	 * Executes a query and kills process (dies)
	 *
	 * @deprecated 1.5.0.1
	 * @param $sql
	 * @param int $use_cache
	 */
	public static function ds($sql, $use_cache = 1)
	{
		Tools::displayAsDeprecated();
		Db::s($sql, $use_cache);
		die();
	}

	/**
	 * Get used link instance
	 *
	 * @return PDO|mysqli|resource Resource
	 */
	public function getLink()
	{
		return $this->link;
	}
}
